RU2665537C2 - Injection-compression apparatus for manufacturing thermoplastic containers - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to an injection-compression apparatus for manufacturing thermoplastic containers. Technical result is achieved by an injection-compression apparatus for manufacturing thermoplastic containers, in particular preforms made of polyethylene terephthalate having a vertical pivot axis. Apparatus comprises a fixed supporting base, a rotary carousel rotating around a vertical pivot axis relative to the fixed supporting base. Plurality of molds for injection-compression of thermoplastic containers are located along the periphery of the rotary carousel. Plurality of lateral feeding conduits for molds for injection-compression rotating with the carousel. Distribution device connecting a fixed supporting base with the rotary carousel in order to provide transportation of molten thermoplastic material. Wherein the apparatus includes a channel, fixed and coaxial with a vertical pivot axis, adapted to have a connection from the inlet to the extruder and from the outlet to the plurality of lateral feeding conduits. Molds for injection-compression from said plurality are assembled together in injection-compression modules with two or more molds for injection-compression in each module. Each injection-compression module has a single lateral feeding conduit. Wherein the injection-compression apparatus is configured to perform a series of steps of the molding process at the same time in two or more molds for injection-compression of each of injection-compression apparatus modules.EFFECT: increased productivity of the apparatus without deteriorating the quality of castings.9 cl, 23 dwg

Description

FIELD OF THE INVENTION

The invention relates to a plant for the production of preformed blanks made of a thermoplastic material, for example, polyethylene terephthalate (PET), by injection molding intended for the manufacture of food containers, in particular bottles.

State of the art

The production of a very large number of thermoplastic containers, in particular bottles, is a process that, starting from raw materials, usually polyethylene terephthalate or PET, allows to obtain finished containers of even particularly complex shapes that are suitable for most of the changing needs of the market and which are especially lightweight and durable even when they are subjected to high pressure at ambient temperature. The transfer of PET, which is in the raw state in the form of granules, into a plastic container can be carried out either using a single-stage process, or using a two-stage process, if desired.

The one-step process is carried out using a single installation in which the transition of polyethylene terephthalate from granules to a preformed preform using the injection step into the molds and the transition from this preform to the plastic container using the stretching step by blowing is performed continuously, without giving the preformed preform cool completely to ambient temperature. Thus, the preformed preform still retains a portion of the latent heat remaining from the injection step, providing significant energy savings since preformed preforms require less heating to return to a suitable blowing temperature compared to the case in which they must be heated starting from ambient temperature.

The so-called two-stage process, in contrast to the previous one, is carried out at two plants, which in general, but not necessarily, are separate: one plant performs the first part of the production process of the container with the transition of PET, located in granules, to a preformed workpiece, i.e. performs the injection step of preformed PET preforms in injection molds. The second part of the process, which converts the preformed billet into a final container in a blow molding unit, using blow-drawing technology, which is generally used today to blow containers of polyethylene terephthalate, is carried out in a second installation. The two-stage process can also be performed on the same installation, which includes the processes of injection of preformed blanks and blowing them into bottles, but the two operations are carried out with time diversity. Preformed blanks are allowed to cool after injection and reach ambient temperature. Subsequently, when preformed blanks are to be converted into finished containers, in particular bottles, they must be heated in appropriate ovens in order to bring them back to the temperature required for a typical process of blowing thermoplastic material used or necessary for drawing by blowing, if PET is used.

One of the reasons why a combined single-stage installation is preferred is that this type of installation guarantees better quality of the final product with less energy consumption, as previously mentioned. Better quality of the final product can be obtained due to the possibility of changing product parameters in real time, adapting them to the production needs of containers in a quick and efficient manner. In addition, in a combined single-stage installation, an error in the production of a preformed preform can be immediately detected, thus allowing the malfunction of a preformed preform and / or a finished container to be corrected.

Instead, in a two-stage installation, a manufacturing defect that occurred with a preformed workpiece during the injection operation can be delayed to be detected, thereby jeopardizing products manufactured in a few days. In addition, the lack of continuity between the two stages prevents the receipt of all life cycle information of the preformed billet, starting from its storage, thus, the stretching step due to blowing is performed without information about the exact characteristics of the preformed billets being processed at any time. No less important is the problem of contaminating preformed workpieces as a result of not being immediately converted to finished containers if they are supposed to contain food, thereby jeopardizing the shelf life of this product.

Blow molding is also preferred at present because it is particularly suitable for creating hollow bodies with a complex shape and many undercuts. Blowing has a great advantage, allowing the production of containers with a body that is much wider than its inlet, such as bottles and flasks. In addition, centrifugal molding is preferred since the production cycle, i.e. cycle time is shorter. Blowing is a particularly fast, efficient production process adapted for the mass production of containers, such as thermoplastic resin bottles, and in particular of a material such as PET for beverages, for which market demands for production are particularly high in quantitative terms. The short cycle time allows you to allocate installation costs to a very large number of produced copies, thus allowing you to achieve productivity that reaches even the order of several tens of thousands of containers per hour in large blow molding plants. Thus, the key element from an economic point of view is the cost of raw materials, for example, PET (polyethylene terephthalate), PE (polyethylene), PPE (polyphenylene), PP (polypropylene), and thus reducing the amount of material used to produce a single container, is critical.

One of the problems that still needs to be overcome in creating single-stage plants is their low productivity compared to two-stage plants, since the first part of the container manufacturing process, which is the process of injecting a preformed workpiece into many mold cavities, is by far the most more common and slower than the second part of the production process, which is the process of drawing due to blowing, and thus the last perazim, which can already be achieved very great potential for high performance, must be made with a capacity which is lower than the maximum possible productivity, to maintain it at the same level as the mold performance for injection preform. The document US20080251974 describes a rotating carousel for the production of preformed blanks, which has as its main characteristic the use of the so-called `` mass-drive '', i.e. centrifugal force system. There is not one of the problems discussed above presented in this document that would not have been presented there, for example, any mention of the problem of how to obtain a high rotation speed. Conversely, a method for changing the rotational speed of a carousel is described (page 4, § 0031) in accordance with the various stages of the duty cycle, which will be poorly set when combined in a single-stage installation. The document US 20080251974 does not allow to solve the problem of how to increase the speed of rotation of the carousel.

A variant of the described technology, which looks most promising from the point of view of productivity and quality of the preformed workpiece, is the use of injection molding technology, which requires less energy consumption for work and less press force to compress the mold of the preformed workpiece. Another advantage of this process is that it exposes the thermoplastic material to less stress, making it possible to produce finished containers with very thin walls, while guaranteeing the high quality of the container. If a rotating platform is used to apply the injection molding production cycle instead of the variable cycle typical of injection molding presses, then an easier way is to combine a preformed blank forming machine with a rotating blower for blowing containers if a combined single stage installation is used. Document WO 2011161649 describes an apparatus for manufacturing a bottle of polyethylene terephthalate, which comprises an injection molding step for creating preformed blanks, followed by an inflating puller for creating finished bottles. The problem that must be solved is how to increase the speed of production of preformed billets in order to effectively combine the two processes: injection molding and drawing by blowing in a single installation. WO 2011161649 proposes the use of electromechanical or pneumatic actuators for actuating molds that can reduce production time.

Thus, there is a need to provide new rotary injection molding machines for creating thermoplastic preformed blanks, in particular made of polyethylene terephthalate, in order to meet the market needs for increasing productivity and reducing the cost of preformed blanks, while at the same time without compromising their quality. Thus, solutions are required to increase the speed of the injection molding machine for preformed blanks without compromising the quality of the manufactured preformed blanks. In addition, there is also a need to increase automation and reduce the time for technical support of the injection molding machine for the production of thermoplastic containers without increasing the complexity or cost of the structure.

Disclosure of invention

An object of the present invention is to provide an injection molding device for the manufacture of thermoplastic containers, in particular preformed blanks of polyethylene terephthalate (PET), which solves the problems mentioned above.

These problems are solved using an injection molding device, which, in accordance with paragraph 1 of the claims, has a vertical axis of rotation Y and contains:

- fixed support base,

- a rotating carousel that rotates around an axis of rotation with respect to a fixed support base,

- a plurality of injection molding molds for containers located along the periphery of the rotating rotary magazine, the above-mentioned plurality of molds being assembled together in compression modules in molds with at least two molds in each module,

- a dispensing device connecting the fixed support base to the rotating rotary magazine in order to allow molten thermoplastic material to be transported, the device comprising a passage channel fixed and coaxial with the axis of rotation Y, adapted so that it has a connection from the inlet to the extruder and from the outlet to at least one transverse feed pipe of the corresponding module for pressing in the molds, while in The aforementioned at least one side supply pipe rotates along with the carousel.

Based on the features of the invention, a rotating carousel can be provided with molds for injection of a preformed workpiece in groups of two, three or four, while offering the following advantages:

- higher productivity in the production of containers, since the carousel can rotate at higher rotation speeds, in relation to installations having molds arranged in different ways, in accordance with a device for distributing molten resin;

- reduced mechanical cycle time for opening and closing the injection molding mold;

- reducing downtime when changing the format;

- the possibility of using robotic systems for disassembling and refitting a machine or its subgroups, in accordance with the modularity of the device architecture;

- the possibility of obtaining higher quality preformed blanks and reducing production waste, in accordance with the accuracy of the dosage of the resin provided by the device during the distribution of resin in each of the molds;

- better centering of the inner part of the mold or punch in the cavity for pressing, which improves the concentricity of the preformed workpiece;

- getting rid of deformations caused by thermal expansions and from typical mechanical stresses of structures with many cavities.

The result is a comprehensive advantage of higher hourly productivity with better quality preformed workpieces.

The dependent claims describe preferred embodiments of the invention, forming an integral part of the present description.

Brief Description of the Drawings

Further features and advantages of the present invention will be better understood in light of the detailed description of preferred, but not exclusive embodiments of the invention, an injection molding device illustrated by way of non-limiting example using the accompanying drawings, in which:

In FIG. 1 schematically shows a production plant for a thermoplastic preformed billet in which an injection molding device according to the invention is integrated, a top view.

In FIG. 2 shows a part of the apparatus shown in FIG. 1, a top view in perspective.

In FIG. 2a is the same side view.

In FIG. 3 shows the installation element shown in FIG. 1 is a sectional view along the axial plane.

In FIG. 3a is the same, enlarged view.

In FIG. 3b shows a detail of the element of FIG. 3 is an enlarged perspective view.

In FIG. 4 shows the installation element shown in FIG. 1, perspective view.

In FIG. 5 is the same, sectional side view.

In FIG. 6 shows another element of the apparatus shown in FIG. 1, perspective view.

In FIG. 7a is the same in the first working position, a sectional view.

In FIG. 7b is the same in the second working position, a sectional view.

In FIG. 8 and 9 show another installation element shown in FIG. 2, in two different operating positions, perspective views on an enlarged scale.

In FIG. 10 and 11 show another element of the apparatus shown in FIG. 1, in two different operating positions, perspective views on an enlarged scale.

In FIG. 12a, 12b, 13a and 13b show a thermoplastic material injection unit integrated in the apparatus of FIG. 1, in various operating positions, sectional views.

In FIG. 14, 15, 16 and 17 show the installation element shown in FIG. 1, in various operating positions, sectional views.

The same numeric numerals and lettering in the drawings refer to like elements or components.

The implementation of the invention

A preferred embodiment of an injection molding apparatus for containers of thermoplastic resin is described below with a separate reference to the above drawings.

In FIG. Figure 1 shows a rotary-type injection molding machine for containers of thermoplastic material, typically preformed blanks made of polyethylene terephthalate (PET) for the manufacture of bottles or other containers for use with food or non-food products.

In this diagram, an injection molding device cooperates with a cooling device 51 of preformed blanks, for example, with a star conveyor 50 provided with grippers 4, for moving the preformed blanks from the rotating carousel 2 to the cooling device 51. This configuration is typical in a container manufacturing plant two-stage type. Those skilled in the art will appreciate that, without departing from the scope of the invention, instead of a cooling device 51 of preformed blanks, the blowing machine can interact with an injection molding device with corresponding auxiliary devices of the type known in the art of the current level, such as conveyor for preformed blanks, cooling and / or conditioning wheels, heating furnaces, etc. If necessary, other machines, such as those used for marking containers and filling them with the product intended for them, can be inserted into the unit.

In addition, the various components of the installation can be either aligned or aligned with the rotation axes, which ideally form a triangle, or more generally a polygon, in order to adapt to the space requirements of the installation location this setting.

The installation of FIG. 1 contains at least one extruder 1 of a known type, the function of which is to plasticize the polymer, converting it from a solid state in granules to a liquid state, with the addition of energy provided by special heaters and friction forces, which are created due to the action of the extrusion screw, such by creating molten resin.

The installation also includes a rotary rotary magazine 2 for pre-molding using injection molding, which can rotate around a vertical axis Y.

A distributor 3 for distributing the molten resin produced by the extruder 1 for each mold located on the outer periphery of the carousel magazine 2 is provided between the extruder 1 and the rotating carousel magazine 2. Since the injection molding device is configured as a rotating carousel magazine 2, the flow rate of the molten feed the resin should be almost constant over time, so preferably an extruder 1 should be used, which is able to create current flow rate.

Rotating carousel 2 with separate reference to FIG. 2 comprises a horizontal lower disk 20 and an upper disk 22 parallel to the lower disk. Both discs 20 and 22 share the same rotation axis Y, forming an assembly with a perfect-shaped drum. A plurality of injection molding molds 9 ′, 9 ″, 9 ″ ″ are arranged along the periphery of the drum, the molds having a substantially oblong shape and each of them defines a vertical axis of sliding Υ ′ (FIG. 4) of the press halves -forms parallel to the Y axis of rotation of the carousel 2, which can rotate, for example, in the direction of the arrow F (Fig. 2), or, if necessary, in the opposite direction.

The lower disk 20 and the upper disk 22 are joined to each other by means of modules 9 for pressing in the molds in such a way as to contribute to the formation of the supporting structure of the carousel 2 with high rigidity, which is thus able to withstand high loads generated during the injection process pressing. The number of injection molding molds is determined during the design phase of the injection molding apparatus, in accordance with a criterion relating to the estimated productivity of the production plant for manufacturing preformed blanks and / or finished containers.

In FIG. 2 shows only two modules 9 for molding in molds, each of which contains three injection molds 9 ', 9' ', 9' '' for the purpose of preserving clarity of presentation, however, it should be understood that the molds 9 ', 9' ', 9' '' occupy the entire periphery of the carousel 2, while they are completely similar to each other and are divided into the number of modules 9, which is three times less than the number of molds.

In particular, the solution of FIG. 2 shows an embodiment of the invention with modules 9 for pressing in molds having three molds 9 ′, 9 ″, 9 ″ ″ along the peripheral surface of the carousel 2; however, modules with a mold number other than three can be used without departing from the scope of protection of the invention. These solutions are not shown in the figures, as they are clear and obvious to a person skilled in the art.

The molten resin distribution device 3, shown in more detail in FIG. 3, 3a and 3b, is provided in the middle of the carousel magazine 2 on the lower disk 20. The distribution device 3 allows the molten resin to be moved from a single supply pipe 10 of a fixed extruder 1 to a plurality of compression modules 9 in molds that rotate with the carousel shop 2.

The distribution device 3 is provided with a rotating connection comprising:

- a fixed structure 3 'provided in the center with longitudinal fixed elements 23 extending along the Y axis, in which a molten resin passage 11 is provided, having an appropriate diameter compatible with the required flow rate of the molten resin, for example from 28 to 42 mm, preferably 32 mm;

- a movable structure, in turn, containing:

- the first Central rotating element 25, located in the upper part of the device 3 for distribution, above the above longitudinal fixed element 23, while the element 25 is combined with the lower disk 20 of the carousel 2;

- the second Central rotating element 102, essentially having a bell-shaped shape (Fig. 3b), located under the first Central rotating element 25 and combined with it, this element is provided by a Central through cavity having a cylindrical shape, while it intersects the upper part of the Central fixed element 23.

The passage channel 11 'for the molten resin is provided in the first rotating element 25 having the same diameter as the passage channel 11 at its first end and is connected to the latter. The passage channels 11 and 11 'are located along the Y axis of the carousel 2; wherein the passage channel 11 is much longer than the passage channel 11 '. The aforementioned passage channel 11 ', in contrast to the channel 11, is provided at its second end with an extension for connection with a plurality of radial transverse channels 52, also provided inside the aforementioned first rotating element 25.

Since during the rotation of the rotary rotary magazine 2, the molten resin tends to partially exit the gap between the fixed structure 3 'and the movable structure 3' 'when the resin passes from channel 11 to channel 11', the labyrinth seal 24 preferably ensures that the molten resin is impermeable between the above fixed structure 3 ′ and the above movable structure 3 ″.

The labyrinth seal 24 is located in the space between the inner surface 101 of the cylindrical passage cavity in the middle part of the second rotating element 102 (Fig. 3b), combined with the first rotating element 25, and the outer surface of the fixed longitudinal element 23. One-way and multi-way spiral groove 103, for example, with two or four passes, preferably provided on the inner surface 101. The helical groove 103 is a helical groove having a helical line inclined in a direction opposite to the direction of rotation of the rotating elements 25 and 102, and thus to the entire rotary magazine 2. Thus, the relative rotational movement of the spirals relative to the fixed longitudinal element 23 creates a pumping effect that counteracts the release of the molten resin under pressure from the gap between the fixed structure 3 'and the movable structure 3' ', squeezing it up and supporting it inside the device 3 for distribution.

In particular, such an oblique helix counteracts the natural direction of flow of molten plastic into the gap along with rotational movement. For example, in the case of rotation of the movable structure 3 ″ in accordance with the direction F (FIG. 2), the helical groove 103 is a left-handed helix. In particular, the gap between the fixed structure 3 'and the movable structure 3' 'has an annular shape with an L-shaped cross section and is limited on one side by the lower surface of the first rotating element 25 and the upper surface of the fixed longitudinal element 23, and on the other side is limited by the inner surface 101 of the rotating member 102 and the outer surface of the fixed longitudinal member 23.

This rotary joint allows a relative relative rotary nozzle to be provided between the fixed longitudinal member 23 and the first rotating member 25. On the other hand, the fixed member 23 is attached to a supporting member 35 that is connected to the structure of the installation. The thrust sliding bearing 26 is inserted between the upper movable structure 3 ″ rotating around the Y axis and the lower fixed structure 3 ’of the distribution device 3.

The molten resin passing from the feed pipe 10 of the extruder 1 passes sequentially into the passage channel 11, the passage channel 11 'and into the transverse radial channels 52. The above transverse radial channels 52 of the first rotating element 25, in turn, are connected with the corresponding transverse pipelines 27, which connect the first rotating element 25 with the respective modules 9 for pressing.

Each transverse conduit 27 is provided with a respective central channel 27 'having a suitable diameter for supplying injection molds 9', 9 '', 9 '' 'with a predetermined amount of molten thermoplastic material. Electrical resistors 38 ', 38' 'and 38' '', adapted to maintain the molten resin at a predetermined temperature so that the resin can reach the modules 9 ', 9' ', 9' '' at a design temperature for pressing previously molded billets, which are preferably arranged along various pipelines intersected by molten resin inside the distribution device 3.

Each central channel 27 'of the transverse pipelines 27 is connected to a distribution pipe 28 (Fig. 12a, 12b, 13a, 13b) located on the injection unit 29, which is connected to the corresponding cavities 41', 41 '' using the corresponding circuit from the channel network 41 '' 'for pressing located on the corresponding module 9 for pressing in molds.

Although in this part of the description, for the sake of brevity, reference is made to a single module 9 for pressing, which is provided by three molds 9 ', 9' ', 9' '', and more precisely, to a single mold 9 ', it will be appreciated that all molds and compression modules in molds that are tilted in the rotary rotary magazine 2 have the same functional and structural features, unless otherwise defined. In the embodiment shown here, the plurality of compression modules 9 are equal to one third of the number of cavities 41 ', 41' ', 41' '' for compression in the molds.

Thus, the module 9 for pressing in molds is described in more detail with reference to, in particular, FIG. 4 and 5. The module 9 for pressing in molds contains a support element, for example, in the form of a frame 21 with a very strong, rigid, essentially C-shaped structure, which is attached as a whole part with its upper part to the upper disk 22, and its the lower part is attached to the lower disk 20. Its rigidity allows you to withstand reactive forces produced by forces interconnected with injection molding. Three molds 9 '9' ', 9' '', which are equivalent to each other and form a module 9, are fixed on the open part of the frame 21, facing in the radial direction to the outside of the carousel 2.

Mold 9 'consists of three parts: the upper part 12, the Central part 13 and the lower part 14.

For the sake of clarity, the upper part 12 is conditionally part of the mold 9 ', which remains attached to the frame 21 of the module 9 during routine maintenance operations or format changes of the cavity 41' for pressing in the molds.

The central part 13 is conventionally part of the mold 9 ', which can be replaced using a relatively simple quick operation, when it must be replaced due to wear or changing the format of preformed blanks to be manufactured. During the current molding operations, the central part 13 remains fixed and integrated into the block with the upper part 12, while both parts 12 and 13 move together along the direction D (Fig. 5) to close and open the compression chamber 41 'for compression molding .

The lower part 14 is conventionally part of the mold 9 ', fixed in one piece with the frame 21, which does not move during the current molding operations and can be replaced using a relatively simple, quick operation when it is necessary to replace the cavity 41' for pressing in the press - forms due to wear or changing the format of preformed blanks to be manufactured.

The upper part 12 contains a longitudinal rod 55, sliding vertically in the guide hole of the upper part of the frame 21, while it is combined at its upper end with a movable block 53, which can slide in the direction of the arrow D, along the guide 54, fixed in one piece with the above upper part of the frame 21. The rod 55 includes a wheel 230, or an equivalent element that acts as an eccentric that can follow the surface of the cam (not shown), while it controls the vertical movement of the upper part 12 and a central portion 13 of the mold 9 'during the molding operation.

A locking and unlocking wedge 57 for locking and unlocking the shaft 55, controlled by a pneumatic actuator 58, allows you to keep the upper part 12 and the central part 13 locked in a lowered position (Fig. 14) due to the impact on the additional wheel 56 provided on the shaft 55 in the time of the pressing stage of the preformed workpiece. When the wedge 57 is removed from a special place in the rod 55 under the influence of the pneumatic actuator 58 (see the position in Figs. 5, 15, 16 and 17), this allows vertical sliding movement of the upper part 12 and the central part 13 to perform other steps molding cycle described hereinafter.

The Central part 13 contains (Fig. 6, 7a, 7b):

- bayonet connection 15 for attachment to the upper part 12, in order to allow quick attachment and detachment of the Central part 13 from the upper part 12, for example, during operations of changing the format of preformed blanks;

- a sliding guide box made up of four rods 16 ', 16'',16''', 16 ^iv , interacting with the respective return springs 200, and fixed in the upper part to the first plate 18 and in the lower part to the base structure 18 ", the first plate 18 is provided with a central through hole 210 through which the rod 55 passes, while the rod is attached at its lower end to the bayonet connection 15, which is provided inside the guide box, allowing relative sliding movement between bayonet connection 15 and the first plate 18;

- a pneumatic cylinder 19 having an internal cavity defining a pneumatic chamber into which the piston 49 is placed. The aforementioned cylinder 19 is attached at the upper end to the bayonet connection 15, possibly with an intermediate extension 220, and is provided at its lower end with a flat part, for example, in the form a second plate 18 ', preferably coinciding with the same flat lower end of the cylinder 19 itself, slipping along four rods 16', 16 '', 16 ''', 16 ^iv ; the above return springs 200, which are helical and coaxial with the above rods, are fixed at their first end to the first plate 18, and at the second end to the second plate 18 ', which is either a single part with a part of the cylinder 19, or belongs to this part of the cylinder, which can move in parallel with respect to the first plate 18;

- a punch or core 59, attached integrally to the piston 49, forming an additional component to the cavity 41 'for pressing in the molds to complete the mold for the preformed workpiece, limiting the internal shape of the preformed workpiece;

- cams 8 ', 8' ', fixed in one piece with the guide element 59' of the punch 59, which are external and coaxial with the latter;

- a base structure 18 ″ to which four rods 16 ′, 16 ″, 16 ″ ″, 16 ^iv are attached, comprising a system of two transverse arms (or swing arms) 67 ″, 67 ″ suspended on respective fingers 68 ', 68''of the base structure 18'', and on which respective pushers 69', 69 '' which follow the cams 8 ', 8''arefixed; while the above levers 67 ', 67''control the opening and closing of two half-sponges or detachable clamps 66', 66 '' (Fig. 7a and 7b), which determine when to close (Fig. 7a), the shoulder defines a negative cavity that forms the neck region of the preformed preform, allowing to complete the closing of the compression cavity 41 ′ in the molds when the preformed preform is to be molded.

The spring 63 inside the cylinder 19 produces a slight thrust on the punch 59 to facilitate the regular filling of the molded resin cavity 41 'for compression in the molds during the first molding step. The bayonet connection 15 shown in more detail in FIG. 10 and 11, comprises a sleeve 60 located around the base 61 of the coupling with a limiter, which allows its angular rotation around the axis Υ ', but is integral with the base 61 of the coupling in the direction parallel to the axis Υ'. The sleeve 60 is provided with teeth 62 ', 62' ', 62' '', directed towards the inside of the cavity, which is shaped so as to fit into the corresponding longitudinal grooves of the longitudinal shaft 55 and slide in the annular groove of the above longitudinal shaft 55 with a relative rotation of about 60 ° between the shaft 55 and the sleeve 60 in the direction of the arrow R. Thus, it is possible to quickly attach and detach the central part 13 from the upper part 12 of the mold 9 'in order to perform assembly / disassembly operations or to change the format and preformed blanks.

The lower part 14 of the mold 9 'contains a cavity 41' for pressing in the molds and a second bayonet connection 64 '(Fig. 8, 9) provided on the supporting frame 21, which interacts with the corresponding sleeve 65 (Fig. 6, 7a ) located on the base of the cavity 41 '. Thus, the speed of replacing the cavity 41 'is guaranteed for technical support or for changing the format.

It should be borne in mind that in order to guarantee a change in the format containing a larger number of preformed blanks, the length of the rod 55 must be provided with at least one extension, which can be either added or removed to achieve the required length. Alternatively or in combination, the aforementioned at least one extension 220 may be located between the bayonet fitting 15 and the cylinder 19 (FIGS. 6 and 7).

When the compression chamber 41 'in the molds is opened, the central part 13 moves upward from the lower part 14, in the direction indicated by the letter D. As soon as the first plate 18 adjoins the upper part of the C-frame with a bumper 17, preferably made of rubber, 21, the rod 55 is further raised by means of a cam surface acting on the wheel 230, thus moving the punch 59 and subsequently the cams 8 ′, 8 ″ in the upward direction due to relative movement relative to the plate 18 with punched holes and, which at this time remains stationary together with the base structure 18 ″, and thus together with the hinge axis 68 ′, 68 ″ that supports the levers or swing arms 67 ′, 67 ″ at the same predetermined distance from the plate 18 s punched holes.

The relative movement of the cams 8 ′, 8 ″ and the levers 67 ′, 67 ″ between them is hindered by the two detachable collars 66 ′, 66 ″ separating them (Fig. 7b) due to the fact that the pushers 69 ′, 69 ″ of the levers 67 ', 67' 'follow the profile of the cams 8', 8 '', releasing the neck of the preformed workpiece, which can be removed from the punch 59 by using special grippers provided on the star conveyor 50. The return springs 201 (Fig. 7a) retain the pushers 69 ', 69' 'in contact with the cams 8', 8 ''. The description made for the mold 9 ′ is repeated in the same way for the molds 9 ″ and 9 ″ ″ of the module 9 for compression in the molds and is omitted here for the purpose of brevity.

The injection unit 29 is described in more detail with reference to FIG. 12a, 12b and 13a, 13b, which show the steps of loading the dose of resin and the steps of filling the cavity 41 ″ for compression in the molds with the dose of resin, respectively, for each molding cycle. Although reference is made to the mold cavity 41 ″, it is apparent that the block 29 has two other mold cavities 41 ′ and 41 ″ ″, preferably equal to the cavities 41 ″ with the same auxiliary components as described for cavity 41 ″, which are filled at the same time.

The resin injected into the compression chamber 41 ″ by pressing the piston 39, sliding in the corresponding metering injector 34, is connected to the hot chamber 30. The piston 39 is driven by a pneumatic cylinder 33, which in turn is controlled by a valve ( not shown in the figures). Where necessary, appropriate heating means are provided, for example, resistive tapes, in order to maintain the resin at a design temperature in various parts of the injection unit 29.

The injection nozzle 31 is located in the upper part of the hot chamber 30 with a vertical axis Y 'and is also heated by an electric resistor, for example a tape type. Such an injection nozzle 31 allows metering of molten material passing into the compression cavity 41 ″ in the molds through the opening 42. Preferably, the aforementioned opening 42 has a diameter of 3-5 mm, preferably 4 mm.

The hot chamber 30 intersects with a first pipe 70 connected to a distribution pipe 28, which receives resin from one or more transverse pipes 27. This first pipe 70 is connected to the second pipe 71 also inside the hot chamber 30 and connects the reservoir 72 of the metering injector 34 with the injection pipe 73 nozzles 31 for injection. The hole 42 either opens or closes during operation using a valve 32.

Preferably, a mechanism with a single actuator for the operation of filling the corresponding cavity for pressing in the molds and for the operation of filling the corresponding metering injector 34 is provided for each cavity 41 ', 41' ', 41' '' for pressing in the molds of each module 9 However, in this embodiment of the invention, there is only one electric valve that controls three pneumatic cylinders 33, and thus, three cavities 41 ', 41' ', 41' '' for pressing in the molds of each module 9 are made are the same step in each cycle the same time. The mechanism that actuates the switching between the filling step of the metering injector 34 and the step of filling the mold cavity may be a valve 36, for example, of a spool or plate valve type, capable of opening or closing the passage for molten resin from conduit 70 in the direction a reservoir 72 for filling the metering injector 34. The above valve 36 is actuated by an actuator 37 located at the first end of the valve 36. The valve 32 is connected behind integral to the second end of the valve 36 opposite the first end. Actuator 37, valve 36 and shutter 32 are longitudinally and preferably along the same axis Υ '.

Actuator 37 comprises two separate cylindrical chambers 74, 75 provided with respective pistons 76, 77 integrated with each other. The lower cylindrical chamber 75 is provided with two inlet / outlet pipes 78, 79 for compressed air.

A round adjusting nut 44 of the position of the support plate 43 of the double-acting piston 40, designed to accurately adjust the dose weight of the molten resin to the nearest hundredths of a gram, is provided in the lower part of the cylindrical chamber of the pneumatic cylinder 33 of the metering injector 34. The position of the above support plate 43 can be set separately for better calibration of the preformed workpiece.

The double-acting piston 40 of the pneumatic cylinder 33 is driven by a combination of pressures and backpressures created by compressed air that is introduced into the upper 45 and lower 46 of the chamber, and also due to the molten resin coming from the extruder 1 through the channel 70 of the hot chamber 30.

During the pitch loading step of the resin into the dispenser, which corresponds to lowering the piston 40 along the direction shown by arrow G, the pressure of the molten resin pushed by the extruder into the reservoir 72 acts on the piston 39 and prevails with respect to the combination of pressures and backpressures generated by the compressed air, which is introduced into the upper chamber 45, is suitably adjusted in the range from 10 to 40 bar, and in the lower chamber 46, always connected to the air circuit, the pressure is preferably 40 bar.

During the injection step of the molten resin corresponding to the rise of the piston 40 along the direction shown by arrow G, a high pressure of compressed air, preferably 40 bar, operates in the lower chamber 46 and comes from the inlet 48, while the upper chamber 45 of the same cylinder 33 is connected by means of a control valve to the low pressure air recovery circuit (0-8 bar) through the exhaust pipe 47.

The coordinated movement of the valve 36, the shutter 32 and the metering injector 34, as well as the calibration of the support plate 43, allows the metering of the amount of molten resin needed to be inserted into the mold cavity 41 ″ in accordance with the design of the preformed workpiece, which should to be made. The coordinated movement of the injection unit is driven by the use of electric valves driven by programmable systems.

In particular, the valve 36 is opened by means of an actuator 37, leaving the pipe 70 open when the piston 39 of the metering injector 34 is in an advanced position, as shown in FIG. 12a. Opening the valve 36 due to upward movement determines the closure of the opening 42 of the injection nozzle 31 with the shutter 32 and the piston 40 of the double acting metering injector 34 retracted by the pressurized front side of the molten resin coming from the hot chamber 30 and filling the reservoir 72.

After the double-acting piston 40 reaches the location of the support plate 43, the loading step is performed and the metering injector 34 is prepared to inject a dose of resin into the mold cavity 41 '' as soon as the appropriate command is issued.

The injection step includes closing the valve 36 by displacing it in the downward direction determined by the actuator 37, and simultaneously opening the shutter 32, which moves downward, thereby freeing the outlet section of the nozzle 31 (Fig. 13a), i.e. the hole 42, followed by forcing movement of the metering injector 34 by means of a double-acting piston 40 (FIG. 13b). The valve 36 closes while the piston 39 of the metering injector 34 advances, and therefore, the molten resin is forced to pass through the conduit 71 and the injection conduit 73 to reach the interior of the mold cavity 41 ″.

Each transverse conduit 27 is provided with two spherical joints 203 (Fig. 3a) at the ends by which it is connected to the distribution pipe 28 on one side and to the rotational element 25 on the other side, in order to compensate for the relative displacements between the lower disk 20 and the rotational element 25 of the distribution device, mainly due to thermal expansion, by rotational displacement. In a plan view (not shown), the transverse conduit 27 is positioned so that it is not precisely aligned in the radial direction with respect to the rotation axis Y. Instead, it is slightly offset relative to the rotation axis Y, i.e. the ideal axis of the pipe 27 ideally never crosses the center of rotation of the carousel 2, but the ideal line, which he defines, runs at a given distance from this center. This arrangement (shown in Fig. 2) allows to take into account the thermal expansion of the transverse pipe 27 in both radial and vertical directions. This arrangement, as explained above, is the same for each transverse conduit 27 of each compression module 9 in the molds of the carousel 2. In an alternative embodiment, each compression module 9 in the molds may include the same number of transverse pipelines 17 as and the number of molds in the module.

According to a preferred embodiment of the carousel 2, the extruder 1 acts as a positive displacement pump to provide a flow rate of molten resin required at the outlet with a preferred pressure between 50 bar and 200 bar. Such pressure is sufficient to move the molten resin within the entire internal channel system of the dispenser 3, the transverse pipe 27 of each mold module 9 corresponding to the hot chambers 30, assuming that their resin can be supplied to the single passage 11 in the dispenser 3 three distribution injectors during each molding cycle in each module 9 for pressing in molds.

The preferred temperature of the molten resin maintained within the system of various channels is 270 ° C. This temperature is guaranteed by controlled electrical resistors located at the required points. At such a given operating temperature of the resin, the dispenser 3 is water cooled to maintain the temperature of the thrust sliding bearing 26 below 80 ° C. In addition, preferably, the entire resin distribution system has an outer coating with a heat insulating material to limit undesired heat loss and improve the energy efficiency of the entire installation.

The star-shaped conveyor 50 moves the manufactured preformed blanks with a plurality of jaws 4 attached to the star-shaped conveyor 50 sequentially from the rotating carousel 2 to the device 51 for cooling the preformed blanks, where they are either cooled or thermally prepared (Fig. 1).

The molding process contains a sequence of steps that are performed at the same time in three cavities 41 ', 41' ', 41' '' for pressing in the molds of module 9.

The first step (Fig. 14) is the step of forming preformed blanks, during which the rod 55 is moved down in the direction D, which controls the punch 59. The mold 9 'is blocked by a pneumatic wedge 57 and high pressure air, of the order of 30-35 bar while the wedge is introduced into the compensation chamber 94 of the cylinder 19. Thus, the molten resin inside the cavity 41 'is exposed to a maintained pressure, which depends on the ratio of the areas of the compensation chamber 94 and the punch 59. cooling is performed by chilled water, which flows in the pipelines provided for these purposes in the mold elements in contact with the resin, i.e. cavity 41 ', punch 59, and detachable clamps 66', 66 ''. During this step, volume recovery due to a change in density due to the thermal effect is also performed by lowering the position of the punch 59 caused by high pressure air in the compensation chamber 94. In this way, pressure is actually increased in the compensation chamber 94 to allow the pressure boosting step to compensate for the compression of the molten resin in the pressing cavity 41 'during the cooling step of the preformed workpiece.

During this step, the spool valve 36 inside the hot chamber 30 opens to allow filling of the reservoir 72 with molten resin.

The second step (Fig. 15) is the step of opening the mold and follows the cycle of cooling and supporting the resin parameters of the preformed workpiece P. In order to remove the preformed workpiece from the cavity 41 ', the mold 9' is unlocked by removing a pneumatic wedge 57 and the rod 55 is lifted along the direction D. The required opening stroke is always constant, and is preferably 300-400 mm, for example 330 mm, and does not depend on the type of preformed workpiece being formed.

At the same time, the metering injector 34 must finish loading for the next cycle and the molten resin in it is maintained at a back pressure of about 10 bar due to the thrust of the pneumatic cylinder 33, which controls the injector. At the end of this second step, the first plate 18 comes into contact with the upper part of the frame 21: the subsequent lifting of the rod 55 is translated into the opening command for the split clamps 66 ', 66' '.

The third step (Fig. 16), defined as the first step of removing the preformed workpiece, is provided for separating the preformed workpiece Ρ from the punch 59 due to the action of split clamps 66 ', 66' ', which hold the neck of the preformed workpiece, at the same time peeling off the workpiece from the punch 59 in a few fractions of a second before the split collars 66 ', 66' 'are separated from each other in the next step.

The fourth step (Fig. 17), defined as the second step of removing the preformed workpiece, is provided for separating the split clamps 66 ', 66' 'from each other and the preformed workpiece падения falling into the space defined between the closed manipulators 90', 90 '' grab 4 from the bottom.

These operations for removing the preformed workpiece Ρ include synchronization using electromechanical means of upward movement of the punch 59 with horizontal movement when opening the detachable clamps 66 ', 66' '. Thus, the presence of the grip 4 (FIG. 15) is guaranteed under the preformed blank when this blank Ρ is released. Subsequently, the movement of the preformed workpiece Ρ by means of the gripper 4 allows the cavity 41 'to be closed again by lowering the shaft 55 during the next step.

In the fifth step, defined as the step of closing the mold 9 'and filling the compression cavity 41', closing the mold 9 'is performed by lowering the movement of the rod 55, followed by the introduction of the punch 59 and the connection of detachable clamps 66', 66 '', which are connected to the inlet of the cone of the cavity 41 '. As soon as the closing of the cavity 41 'is completed, the pneumatic wedge 57 is inserted into the blocking position of the mold 9', applying a force of about 2-3 tons, as required; this force is controlled by changing the air pressure, which is introduced into the pneumatic actuator 58.

This fifth step corresponds to the step shown in FIG. 14, but without the presence of molten resin in the mold.

As soon as the mold 9 'has been guaranteed to be closed, the shutter 32 of the nozzle 31 is opened by means of an actuator 37. The pipe 70 is closed by the valve 36 at the same time that the shutter 32 is opened. Thus, the pressing cavity 41' is filled by emptying the reservoir 72. The molten resin enters the cavity 41 ', pushed by a double-acting piston 40, exerts a pulling force in the upward direction to the punch 59, which is retracted since it is held in position at this point in time due to the urging spring 63 (FIG. 7a) with a limited force of about 200 N. The molding cycle for the preform begins and ends with the first step described above with the introduction of high pressure air into the compensation chamber 94.

The rotational movement of the various wheels of the installation is synchronized using electromechanical means, since the grippers 4 require very high accuracy of synchronization, so that they are in the correct position for gripping the preformed blanks Ρ from the molds 9 ', 9' ', 9' ''. The main embodiment of the invention includes preformed blanks P sequentially removed by grippers 4 one after the other from each mold, while the injection of molten resin into the mold is performed in groups of three molds, with a time offset between opening the first cavity for pressing in the molds of the module and opening the third cavity for pressing the same module is very short, and thus negligible for purposes of greater or lesser stub lnosti in the mold and the solidification of the preform.

In particular, in the circular sector of the rotating carousel 2, for example, with an angle of about 60 ° in the middle part, means are provided for raising and lowering (not shown) the rods 55 of the molds 9 ′, 9 ″, 9 ″, which include to the aforementioned circular sector during rotation of the carousel 2 with respect to the axis Υ. In the inlet of the aforementioned circular sector, the rod 55 of the mold 9 'is lifted using a wheel or pusher 230 (Fig. 4), which follow the cam surface of the above means for raising and lowering the rod along the direction D. Thus, the cam surface is configured in the first a queue for controlling the vertical upward movement of the rod 55 in the inlet of the above circular sector, and then the vertical downward movement of the rod 55 in the outlet of the above circular sector. The second step of opening the mold 9 '(Fig. 15), the third step (Fig. 16) and the fourth step (Fig. 17) of removing the preformed workpiece Ρ from the mold 9' is performed while the mold 9 'is passing along arcs of a circle bounding the above circular sector.

In the described embodiment of the invention, in which the module 9 for pressing in molds consists of three molds 9 ', 9' ', 9' '', each injection molding cycle is applied to the module and three preformed blanks that are formed in same time. When the pressing module 9 extends into the aforementioned circular sector, the three grippers 4 of the star conveyor 50 (FIG. 1) sequentially enter the opening space between the central part 13 and the lower part 14 of the three respective molds 9 ', 9' ', 9' ' 'to capture the corresponding preformed blanks Ρ and move them sequentially to the cooling device 51.

All steps are controlled by corresponding cams (not all cams are shown in FIG.), Designed in such a way as to transmit the required movements to all components of the mold.

The cooling step of the preformed workpieces Ρ by means of the cooling device 51 is provided at the end of injection molding operations.

In a preferred, but not exclusive embodiment, the number of injection molding modules 9 is from 24 to 32, with a total number of molds 9 ', 9' ', 9' '' between 72 and 96, with three modules being provided for each module Press forms.

In FIG. 1, an extruder 1, a rotating carousel 2, a star-shaped conveyor 50, and a cooling device 51 are arranged substantially in plan along the longitudinal axis. Alternatively, such components may be arranged in such a way as to determine in terms of a L-shaped configuration or a configuration in the form of the Latin letter Ζ. In all cases, in order to replace the central part 13 of the molds, the manipulator 240 of the robot 250 can act on at least one of the two free sides of the four sides of the rotating carousel 2 to disconnect the bayonet connections 15 from the respective rods 55 of the press forms of module 9 for pressing.

To allow this disconnection, a rod lifting system 55, for example of a pneumatic type, configured to lift three rods 55 of three molds together, is provided in a single injection molding module 9, preferably provided on at least one of the two free sides rotating carousel 2. Once the rods 55 have been lifted, and thus, once the molds have been opened by releasing the central portion 13 from the lower portion 14 containing the cavity for the injection molding In addition, it becomes possible to replace the central part 13 with another one having, for example, an elongation 220 of various lengths.

The elements and features illustrated in various preferred embodiments of the invention of the device can be combined without departing from the scope of protection of the invention.

Claims (21)

1. An injection molding device for the production of thermoplastic containers (P), in particular preformed blanks made of polyethylene terephthalate (PET), having a vertical axis of rotation (Y), comprising: - fixed support base, - a rotating rotary magazine (2), which rotates around a vertical axis (Y) of rotation relative to a fixed supporting base, - many molds (9 ’, 9’ ’, 9’ ’’ ’) for injection molding of thermoplastic containers (P) located along the periphery of the rotating carousel (2), - a lot of transverse feed pipelines (27, 52) of injection molds (9 ’, 9’ ’, 9’ ’’ ’), which can rotate along with a rotating rotary magazine (2), - a distribution device (3) connecting a fixed support base with a rotating rotary magazine (2) in order to allow molten thermoplastic material to be transported, the device comprising a passage channel (11), fixed and coaxial with the vertical axis of rotation (Y), adapted so that it has a connection from the inlet to the extruder (1) and from the outlet to the plurality of transverse feed lines (27, 52), characterized in that injection molds (9 ’, 9’ ’, 9’ ’’ ’) from the indicated set are assembled together in injection molding modules (9) with two or more injection molding molds in each module, each injection molding module (9) has a single transverse feed pipe (27), wherein the injection molding apparatus is configured to carry out the sequence of steps of the molding process at the same time in two or more molds (9 ’, 9’ ’, 9’ ’’) for injection molding each of the injection molding modules (9). 2. The device according to claim 1, in which the aforementioned single transverse feed line (27) defines an ideal straight line located at an oblique angle having a value other than zero with respect to the segment of the radial straight line connecting the vertical axis of rotation (Y) and the point of attachment of the transverse feed pipe (27, 52) to the injection molding module (9). 3. The device according to claim 1, in which each module (9) for injection molding preferably has a vertical supporting frame (21) C-shaped. 4. The device according to claim 1, in which the aforementioned switchgear (3) comprises a rotating connection between the passage channel (11) and the aforementioned plurality of transverse supply lines (27, 52) in order to allow the rotation of the plurality of transverse supply lines (27, 52 ) around the vertical axis (Y) of rotation. 5. The device according to claim 4, in which the above transverse feed lines (27) have a corresponding central channel (27 ') having a suitable diameter for feeding the molds (9', 9 '', 9 '') for injection molding with a given amount of molten thermoplastics. 6. The device according to claim 5, in which the aforementioned central channel (27 ') is connected to a distribution pipe (28) available on the injection unit (29), which is connected through the pipeline system loop to the corresponding cavities (41', 41 '', 41 '' ') for injection molding located on the corresponding injection molding module (9). 7. The device according to claim 1, in which each module (9) for injection molding has three injection molds (9 ’, 9’ ’, 9’ ’’) for injection molding. 8. The device according to claim 1, in which the number of modules (9) for injection molding is from 24 to 32. 9. Production plant for the manufacture of thermoplastic containers (P), in particular preformed blanks made of polyethylene terephthalate (PET), sequentially containing: - at least one extruder (1) producing molten thermoplastic, - a device for injection molding having a vertical axis (Y) of rotation, according to any one of paragraphs. 1-8, for injection molding the above thermoplastic containers, a transfer wheel (50) provided with grippers (4) for removing thermoplastic containers from the above injection molding device, - an optionally added cooling device for cooling thermoplastic containers removed from the injection molding device.

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